package com.scnu.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util {

    private static String byteArrayToHexString(byte b[]){
        StringBuffer resultSB = new StringBuffer();
        for(int i = 0; i < b.length; ++i)
            resultSB.append(byteToHexString(b[i]));
        return resultSB.toString();
    }

    private static String byteToHexString(byte b) {
        int n = b;
        if(n < 0)
            n += 256;
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigits[d1] + hexDigits[d2];
    }

    public static String MD5Encode(String origin, String charsetname){
        String resultString = null;
        try{
            resultString = new String((origin));
            MessageDigest md = MessageDigest.getInstance("MD5");
            if(charsetname == null || "".equals(charsetname))
                resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
            else
                resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
        } catch (NoSuchAlgorithmException | UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return resultString;
    }

    private static final String hexDigits[] = {"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
}
